THE HUMAN FEMALE REPRODUCTIVE SYSTEM
THE PATH THE EGG TRAVELS
Ovary
Oviduct or Fallopian Tube
Uterus or Womb
Cervix
Vagina
PARTS OF THE FEMALE REPRODUCTIVE SYSTEM
Ovary
There are ovaries (female gonads)
Produces eggs or ova (female gametes), female sex (oestrogen and progesterone) that regulate the menstrual cycle, pregnancy, and the secondary sexual characteristics (e.g. )
Puberty is the time during teenage years when females start to release eggs. Puberty occurs a couple of years for females than males usually
Menopause is the time when females releasing eggs. This usually occurs between 45 to 55 years of age.
At birth, females have all their eggs formed, but in an immature state
After puberty and before menopause, one egg is released about every days from each ovary
Oviduct or Fallopian Tube
Connects between ovary and
Place where conception or fertilisation of an egg by a occurs
Uterus or Womb
Strong muscular and elastic organ where an unborn develops
After an egg is released from the ovary, a blood-filled lining develops on the walls of the uterus in preparation for the nourishment of the unborn baby. If no fertilisation of the egg occurs, then this lining passes out through the vagina over several days as ‘periods’ or
Cervix
The opening between the uterus and the vagina
During pregnancy, a mucous plug forms across the cervix separating the uterus from the outside to prevent of the unborn baby.
Vagina
Place where the is inserted during sexual intercourse
An elastic and muscular organ that during birth to allow for the passage of the baby
THE FEMALE MENSTRUAL CYCLE
The menstrual cycle begins at and ceases at menopause.
It takes about days.
Menstruation is regulated by the female sex hormones, oestrogen and
Menstruation – Menstruation or ‘periods’ is the release of the blood-filled lining of the uterus if a woman is not pregnant. It begins on Day 1 when menstruation or ‘periods’ begin, and lasts about days.
Ovulation is the release of the egg from the ovary between about Days 12 to 16.
A woman will become pregnant if fertilisation (the of the egg and the sperm) occurs several days after ovulation when the egg is in the fallopian tube. During pregnancy, menstruation
Role of hormones in the menstrual cycle - The Hypothalamus in the brain stimulates the pituitary gland in the brain to produce the hormone FSH (Follicle-Stimulating Hormone). FSH stimulates the growth of an egg in the ovary. The follicle in the ovary secretes oestrogen which stimulates the repair of the uterus wall after and it also stimulates the pituitary gland to produce LH (Lutinizing Hormone). This prevents more than one follicle from developing. LH induces ovulation (release of the ) and the development of the follicle into the corpus . The corpus luteum secretes progesterone. If a female becomes pregnant, the corpus luteum will secrete gonadotrophin which allows the corpus luteum to continue producing progesterone which stimulates the growth of the uterus wall, by inhibiting LH and FSH. If the woman does not become pregnant, the corpus luteum , which leads to less production of progesterone and oestrogen, and menstruation will occur, and another menstrual cycle begins because the lower progesterone and oestrogen levels will stimulate the gland in the brain to produce FSH.
OESTRUS CYCLE IN OTHER ANIMALS
Oestrus is a time when a female animal demonstrates the intensity of the sexual urge. She is said to be ‘in ’. Changes in the lining of the vagina and uterus also prepare for the fertilised egg. Oestrus occurs about the time of ovulation. Female cats and dogs have 2 oestrus periods per year, whereas rats can have them every 5 days.
FERTILISATION OR CONCEPTION
After sexual intercourse, the sperm travels up to join with the egg in the fallopian tube.
The single-celled fertilised egg is called a
23 chromosomes of the sperm and 23 chromosomes of the egg combine in the zygote’s nucleus, so that the developing baby has chromosomes.
INTERNAL AND EXTERNAL FERTILISATION IN ANIMALS
Internal Fertilisation occurs when the male gamete joins with the female gamete inside an organism (e.g.in ). An advantage is that the survival rate is higher, but the number of offspring is
External Fertilisation occurs when the male gamete joins with the female gamete outside the organism (e.g. fish). This often occurs in a environment, many offspring are produced, but there is a low survival rate.
GESTATION OR PREGNANCY
Gestation in humans lasts about 40 weeks or months
The first sign that a woman is pregnant is usually of menstruation (‘no periods’)
After fertilisation in the fallopian tube, the zygote multiplies to form a ball of cells which travels down to the uterus
The ball of cells (embryo) implants into the wall of the
At the place where occurs, an organ called the placenta develops
The umbilical cord grows between the and the unborn baby’s navel
Inside the umbilical cord are blood vessels which provide nutrients and oxygen to the baby, and return wastes such as back to the mother's bloodstream
As the baby grows, it is called a foetus
The foetus is by amniotic fluid inside an amniotic sac
In the ninth month of pregnancy, the foetus turns upside down, and the mother’s breasts enlarge ready for production
BIRTH
At about 9 months, the ‘plug’ at the cervix releases, the sac breaks and fluid comes out through the vagina (‘breaking of the waters’)
Muscular contractions occur to both dilate the and ‘push’ out the baby first from the uterus
Further muscular contractions expel the (‘afterbirth’)
The umbilical cord is cut close to the baby’s navel
The mother begins breast milk production
The mother begins the cycle again after the lining of the uterus from the pregnancy has been expelled over several days
Breech Birth occurs when the baby is born legs first
Caesarean Birth is the removal of the baby from the mother’s uterus
Twins - Identical Twins (i.e. 2 sisters or 2 ) form when one egg and one sperm join, but as the zygote multiplies to form a ball of cells, the ball . Non-identical or Fraternal Twins are formed when eggs are fertilised by 2 sperm.